Spider Ballooning: Can spiders fly?

An aircraft mounted with insect trap in the early 90’s caught over 25,000 specimens of flying insects part of which included spiders of all sorts and varieties, including fishing spiders!

This experiment further highlighted the century old claim of an English naturalist about spiders miraculously boarding a HMS beagle that was several miles away from the seas.

Not only that, it also made one thing clear about spiders, that they could actually fly! But how they did so always remained a mystery until a research in 2018 came to put things into a clearer perspective.

In this article, we take a deep and satisfactory look at spiders and their flight capabilities.

Can spiders fly? 

Yes, some species of spiders can fly although the ones that do so are mostly spiderlings (baby spiders). These spiders use their silky cobwebs to launch themselves into the air and this behavior has been observed as far back as the 19th century, or maybe even farther than that.

New research in 2018 has shown that spiders are actually able to become airborne by using the earths constant electric field to their advantage, contrary to the popular and previously held notion that spiders are ONLY able to fly because they employ the vertical wind speed gradient or convective air current to do so. 

How do spiders fly?

Not all species of spiders fly, and the ones that do so certainly don’t use wings.

Morphologically, spiders don’t even have flight feathers or flight aids of any sort attached to their backs to enable them fly.

Instead, they use the fibrous strand(s) of silks also known as gossamer threads, which they extrude from the region under their abdomen to serve as reverse-parachute and cause them to become airborne.

This phenomenon known as ballooning or kiting has been observed for centuries by scientists and naturalists, and the observers as at then were only able to speculate and were not able to prove how these flights were even possible in the first place.

Spiders were confirmed to have flight abilities in a research funded by the United States Department of Agriculture in the early 1990’s. In the experimental research, aircrafts were mounted with insects traps and flown for 1,536 hours; a timespan which stretched five years and consisted of 1,385 flights, at altitudes of 200, 500 and 15,000 feet in areas of Louisiana and mexico.

Over 25,000 specimens were caught during the experiment which consisted of flies, butterflies, moths and of course spiders.

This research came nearly a century after the young naturalist Charles Darwin claimed to have discovered lots of tiny red spiders, spanning millimeters wide in the deck of a HMS beagle 60 miles off shore.

Since the experiment, the leading theory until 2005, was that spiders relied heavily on the earths atmospheric breeze to become airborne. But this theory was disproved by a research in 2018 which showed that spiders are able to detect the earths electric field and actually use it to shoot into the air at will, even in the presence of no air at all. 

Regardless, this new development is in no way the final stop concerning the centuries-old puzzle, and the possibilites of both drag force (breeze) and electric field could actually be the real explanation. Who knows?

How spiders prepare to fly

Spiders planning to glide through the air usually climb to the highest platforms in their habitat: twigs, leaves, fence pole, tall trees, branches, stones, and sometimes blades of grasses. Because they have the most electric field.

While there, they anchor themselves in position using silks from their abdomen, and then raise two front legs into the air to test for flight conditions. Spider legs are known to have tiny sensory hairs called trichobothria, which are sensitive to both wind and electrical conditions. They normally become ruffled under their influence, much like the influence a rubbed balloon has when brought close to the hair.

If based on the test, the flight conditions are favorable, they begin to tiptoe on their back legs which elevates their anchored abdomens slightly. Then, they release several strands of “reverse-parachutes” silks from their spinneret into the air and break loose of the anchor silk holding them. This cause them to be carried away into the air at the mercy of the winds.

Spiders can take aloft with a single strand of silk (the material is actually very strong) or using numerous of them. Often, the larger the individual the more strands of silk needed to become airborne.

While airborne, spiders likely use their legs to steer, balance and control their speeds. Windblown spiders may use another silk to anchor themselves and bring their journey to a stop, but they normally just let the wind disperse them to a new habitat.

The speed and height when they become airborne varies greatly with the prevailing wind conditions and the drag (air friction) of their parachute silk.

Spiders have been found to travel distances upto 1000 miles and attain heights upto 16 kilometers above sea levels. They are also able to survive 25 days or longer without eating anything while traveling.

Most spiders that have been observed to fly are those of the smaller species or spiderlings of bigger species.

Bigger adults rarely thrust themselves into the air, and whether or not they are even capable of doing so still remains a mystery.

In cases when they do, like the adult females of the Stegodyphus species weighing around 100 mg and stretching 0.5 inch across, and also the European garden spiders and Dolomedes fishing spiders both stretching over 2 inches across, they often support their weight using tens to hundreds of silk strands that can span 1 meters across and in length.

A vast majority of spiders that take to the air mostly do not make it alive before they reach their new habitat. They either die of harsh weather conditions or are collected by hungry and irate predators to be eaten as snacks.

How are spiders able to fly? The theories

There are two hypothesis in the history of science that have been used to explain how spiders seamlessly defy gravity and wander into the air like thin dust. These hypothesis are:

  1. Wind hypothesis (old)
  2. Electric field hypothesis (modern)

Let’s take a closer look at each one of these hypothesis to understand them better.

Wind hypothesis

The wind hypothesis has been around since the nineteenth century and many scientists adopted it as a possible explanation to the spider flight mystery. But the discovery and proof of the electricity hypothesis in 2018 (although speculated since the 1800’s) has caused it to loose grounds.

The wind hypothesis

The wind hypothesis basically theorize that spider ballooning (or flight) works because the silk strands that spiders extrude catches on the wind and drags them along with it.

So there has to be wind, whether strong or light breeze in order for spiders to be able to fly. But, we know from experiments today that the above statement isn’t true at all, as spider flights have been observed even at windless conditions in the lab.

As further disproof to this hypothesis, spider ballooning is known to occur only in light wind situations in the natural environment, and the process is quick and characterized by pace.

It’s just impractical that the soft breeze is responsible for the fast paced acceleration observed during take-offs, and also the aerial lifting of larger species of spiders like the fishing spiders. Heavy breeze can do this, but soft breeze? There has to be some explanation!

Electric field hypothesis

This theory is the modern hypothesis that is now believed to be the explanation behind the spider flight problem. It was first proposed in the nineteenth century but wasn’t given much attention due the earlier wind hypothesis which seemed more reasonable as an explanation.

Later in 2013, the file of the forgotten electricity theory was dusted and looked into by a physicist who felt the wind theory wasn’t sufficient enough to explain the mystery of the spider flight.

He tried his best to look into the matter and later put forth a paper for anyone who was interested. By 2018, Moorey and Doodey had come up with a plausible explanation after building on from the research put forth in 2013. 

The electricity hypothesis

To get this theory, you first need to understand that the earth (even at normal weather conditions) has electricity all around it.

The planet surface has a constantly negative charge while the atmosphere above has a positive charge, and together, these two attract each other and cause an electric field to occur. 

When the spider is at the higest platform around its habitat; on a plant leaf or twigs, the electric field there is the strongest. When the silk comes out of the spiders body, it aquires a negative charge similar to that of the ground, which causes it to quickly repel the ground and thus set the animal aloft.

If there are more than one strands, the various threads will repel one another and also repel the ground surface which bears similar charge as them.

The silks simultaneously would be attracted to the atmosphere which is positively charged. Under this condition, the spider is able to take into the air at extraordinary pace (for its standards) that would’ve been impossible to achieve with light convective current alone.

Why do spiders fly?

Spiders defy the principles of gravity in order to escape flood, predators, or to find a new habitat or move away from competition.

Very few percentage of spiders traveling by air actually make it to their destination though, for the reasons that we have outlined above. 

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Cite this Article (APA Format)

Bunu. M. (2020, May 12). Can spiders fly?. Retrieved from http://emborawild.com/can-spiders-fly/

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